The present invention relates to a radio controlled timepiece that acquires information by receiving radio waves from positioning satellites.
There have been electronic clocks (radio controlled timepieces) that receive radio waves containing date and time information and location information, and perform date and time correction, time zone setting, and the like. Performing such operations in accordance with movement of a user, a lapse of a predetermined time, and the like, a radio controlled timepiece readily and accurately counts the date and time, and can display the local time in accordance with the current location of the user.
There are positioning satellites according to GNSS (Global Navigation Satellite System) as one type of information source that radio-transmits date and time information and location information from outside by radio. Radio waves from positioning satellites can be received anywhere in the world as long as the sky is visible. Accordingly, there are only a few restrictions on such radio waves, and such radio waves are preferably used in portable radio controlled timepieces.
Meanwhile, to receive radio waves from positioning satellites, a much larger load is normally required, compared with the electrical load necessary in a counting operation or a display operation to be performed in an electronic clock. In a portable radio controlled timepiece, or particularly a wristwatch, a power supply that readily copes with a large load cannot be used, as the small size and the light weight need to be maintained. In view of this, technologies have been developed for reducing power consumption by shortening the time required to receive radio waves from a positioning satellite in various manners.
However, if an upper limit is set on reception periods, the possibility that information can be successfully acquired becomes lower. In view of this, JP 2010-60456 A discloses a technology by which the reception-restricted time is varied depending on the intensity of reception from a positioning satellite, and any extension of the reception-restricted time is not allowed when the remaining battery level is low.
Even when the reception level is high, information is not necessarily acquired successfully in a short time, due to temporary noise or the like. When the reception level is low, on the other hand, even if information is successfully acquired, its precision might be too low and cause a problem in practical use. In such cases, there are only low possibilities that information can be successfully acquired in spite of long reception periods, and failed information acquisition is likely to consume electric power for nothing.
The present invention relates to a radio controlled timepiece that can efficiently acquire information from positioning satellites.